hc4361: Reporting to the police that somewhere is a drug den wouldn't be enough for them to obtain a warrant; clearly the person in question wasn't smart enough to 'think it through'.
Unfortunately it is easier than most people think (especially if you know how and where look) to find someone on online forums. I posted photos on my private website which was traced to my address (it was actually a forwarding address) and I got a card from a lovely ab'er :) I never even gave my details out - they just found them by doing a website lookup. It is rather scary for people who aren't aware of how dangerous the internet can be.